Size of the Tumor and Pheochromocytoma of the Adrenal Gland Scaled Score (PASS): Can They Predict Malignancy?

Background Size can predict malignancy in adrenocortical tumors, but the same extrapolation for pheochromocytomas (PCC) is controversial. The goal of this study was to find a correlation between the tumor size and malignant potential of PCC and determine whether the "Pheochromocytoma of the adrenal gland scaled score'' (PASS) proposed by Thompson can be applied to predict malignancy. Methods A retrospective analysis of patients with PCC operated on from 1991 to 2007 revealed 98 PCC removed from 93 patients. Tumor size was available for 90 tumors. Six (6.4%) patients had proven malignancy. Five familial cases were excluded from the PASS analysis. Results Of the benign cases, none developed recurrence or metastasis. There were 54 (60%) tumors > 6 cm and 36 (40%) tumors <= 6 cm. All 12 PASS parameters were individually present in higher frequency in the >6-cm group; but the difference was not statistically significant except cellular monotony (p = 0.02). Overall, a PASS <= 4 was found in 57 patients. Mean PASS was statistically significantly higher in the >6-cm group (4.4 vs. 3.3, p = 0.04). Of the sporadic benign cases, 21 (41%) patients with tumor size > 6 cm had a PASS of >4, and none of them developed metastasis. PASS <= 4 was found in 25 (81%) PCC in the <= 6-cm group, and none developed metastases. PASS >= 4 was found in six (19%) patients in the <= 6-cm group, and none developed metastases. 68 patients completed 5-year follow-up, and the remaining had a mean follow-up of 28.7 months. No correlation was found between tumor size and PASS > 4 and PASS <= 4 (7.8 cm vs. 7.1 cm; p = 0.23). Conclusions Presently there is not enough evidence to indict a large (>6 cm) PCC as malignant. Furthermore, PASS cannot be reliably applied to PCC for predicting malignancy.